Blockage of human arteries is a widespread malady and, as such, represents a significant health concern. Blockages reducing blood flow through the coronary arteries to the heart can cause heart attacks, while blockages reducing blood flow through the arteries to the brain can cause strokes. Similarly, arterial blockages reducing blood flow through arteries to other parts of the body can produce grave consequences in an affected organ or limb.
The build-up of atherosclerotic plaque is a chief cause of arterial blockages reducing arterial blood flow. Consequently, several methods have been introduced to alleviate the effects of plaque build-up restricting the arterial lumen. One such method is a procedure termed angioplasty, which uses an inflatable device positioned in the artery to dilate the lumen at the stenosis. A typical angioplasty device is disclosed in U.S. Pat. No. 4,896,669 to Bhate et al. The angioplasty device of Bhate et al includes an inflatable balloon which is attached to the distal end of a hollow catheter. The proximal end of the catheter is attached to a fluid source, providing fluid communication between the balloon and the fluid source.
To treat an arterial stenosis, a guide wire is first advanced through the artery past the stenosis. Then, a balloon such as the Bhate et al balloon is introduced into the artery in a deflated state and guided through the artery over the guide wire to a position adjacent the stenosis. Fluid from the fluid source is then infused into the balloon via the catheter to inflate the balloon. As the balloon expands, it dilates the lumen of the artery. The balloon is then deflated and removed from the artery.
While effective for dilating the lumen at the stenosis, angioplasty devices, such as the Bhate et al device, do not remove the plaque from the artery. Consequently, the residual plaque either remains in place at the point of the stenosis or breaks off and migrates to other locations in the blood stream. In either case the plaque remains a continuing threat to create blockages in the circulatory system. To address the shortcomings of angioplasty, a procedure termed atherectomy has been devised which cuts and removes the plaque comprising the stenosis from the blood vessel.
An atherectomy procedure typically includes inserting a guide wire into the affected artery and advancing a hollow cutting device over the wire until the cutting device is positioned adjacent the stenosis. The cutting device is then advanced into the stenosis to cut a channel through the plaque, thereby increasing blood flow through the artery. The resulting plaque fragments are removed from the blood stream by drawing them into the hollow cutting device.
A number of atherectomy devices capable of performing this procedure are known in the art. U.S. Pat. No. 4,895,166 to Farr et al, which is assigned to the same assignee as the present invention, discloses an atherectomy device having a frustum-shaped cutter which is attached to the distal end of a hollow catheter. The cutter has two openings that define two straight, even cutting blades. The cutter is directed through the artery over a guide wire, and it is rotated as it advances into the stenosis, thereby cutting the plaque. Excised plaque enters the openings of the cutter and is subsequently removed through the hollow catheter.
A particular problem associated with angioplasty and atherectomy procedures is in moving the guide wire through the stenosis so that an inflatable balloon or cutting device can be positioned within or adjacent to the stenosis. A stenotic segment of a blood vessel presents a narrowed and often tortuous path through which the guide wire must be advanced. In some cases the stenotic segment of the blood vessel may be almost completely blocked (i.e. occluded) with atherosclerotic plaque. If the distal end of the guide wire contacts the stenosis at a location where there is no opening, the guide wire distal end must be moved laterally to find an opening, or an opening must be created. Some currently known systems oscillate or vibrate the guide wire longitudinally to cause the distal end of the wire to create an opening with a kind of picking action. The success of this maneuver depends upon the wire being stiff enough to penetrate the stenotic material. The longitudinal oscillations are not very efficient at moving the distal end of the guide wire laterally to seek out an existing opening.
In addition, as the guide wire passes through the blood vessels, it must pass through numerous turns and curves. At each turn, or even at a slight curve, the guide wire lies in direct contact, over an appreciable extent of its length, with the blood vessel wall. Indeed, the guide wire is in direct contact with the blood vessel wall over a significant part of its inserted length, and the force of contact with the wall is increased at turns and curves. This contact also occurs between the side of the wire and the stenotic material as the distal portion of the wire passes through the stenosis. Once the wire begins passing through the blood vessel, contacting the wall at a given location, it tends to remain in continual contact with the wall at that location, during most of the period of time while wire insertion is being accomplished. Therefore, as the physician advances the guide wire through the blood vessel, it drags on the vessel walls, over much of its inserted length, and this drag is experienced essentially continually during the wire insertion procedure. This means that every minute increment of advancement attempted by the physician is resisted by frictional drag over much of the length of inserted wire. This drag, resulting from friction between the wire and the wall or between the wire and the stenosis, is a significant contributor to the difficulty in advancing take guide wire through the blood vessel, and ultimately through the stenosis.
Systems which attempt to assist in advancing the guide wire by vibrating or oscillating the wire longitudinally do not alleviate the frictional drag problem, because the longitudinal vibrations or oscillations of the wire do not reduce the physical extent of contact between the wire and the wall, and they do not reduce the time of contact between the wire and the wall. At best, the longitudinal vibrations create a continual sliding contact between the wire and the vessel wall. Accordingly, the present invention recognizes the need, in the treatment of an occluded or narrowed blood vessel, for a method of lessening the frictional drag on the blood vessel wall to assist in moving a guide wire easily through the blood vessel. The present invention also recognizes the possibility of reducing this frictional drag by reducing the physical extent of contact between the guide wire and the vessel wall, and by reducing the time of contact between the wire and the wall. Both the physical extent of contact and the time of contact are reduced by introducing whip like transverse vibrations into the guide wire.
It is therefore an object of the present invention to provide a method for advancing a guide wire by transversely vibrating the guide wire such that the guide wire can be more easily moved through a blood vessel and through a stenotic segment of a blood vessel. It is another object of the present invention to provide a method that is especially adapted for use in angioplasty and atherectomy medical procedures. It is a further object of the present invention to provide a method for advancing a guide wire that is relatively easy and cost effective to perform.